Oil rigs can be designed to facilitate transporting the rigs from one well location to another. For example, land-based oil rigs may be made of several sub-components that are sized to fit onto trailers and travel on roads from wellsite to wellsite. When received at a wellsite, the sub-components are assembled together as part of a “rig-up” sequence, ending with the rig ready to drill.
Such transportable rig sub-components often include a substructure, a rig floor, and a mast, among others, which may themselves be disassembled into smaller components. For example, the substructure may include a pair of base boxes, connected together by a spreader. The rig floor is supported by the base boxes, and the mast is supported by the rig floor. Rig-up sequences can include attaching the mast to the drill floor, and raising the mast from a horizontal orientation to a vertical orientation. Before or after raising the mast, the rig floor is lifted upwards on the substructure (e.g., by expanding the base boxes), providing room for a cellar around and immediately above the wellhead. Recently, some rig designs, such as those commercially available from SCHLUMBERGER, have provided mast and substructure raising cylinders (MSRCs), e.g., one per base box, which are capable of raising the mast and raising the rig floor in sequence.
Rigs also provide a setback, where the lower ends of stands of drill pipe are supported when in the rack. The setback is often on the rig floor, and thus elevated therewith and clear of the substructure. However, in some applications, the setback may be positioned on the ground, e.g., at the spreader. In these cases, the positioning of the MSRCs may interfere with the setback, which can present a challenge to operation and rig-up.